1. Field of the Invention
The present invention relates to a 3GPP universal mobile telecommunication system (UMTS) system and, more particularly, to method for transmitting control information of a high speed shared control channel (HS-SCCH).
2. Background of the Related Art
In general, a UMTS system of third generation partnership project (3GPP) supports a new high speed downlink shared channel (HS-DSCH) in order to support a high speed packet data service. The HS-DSCH is used in a system following a Release 5 which specifies a high speed downlink packet access (HSDPA) among the technical specifications of 3GPP.
Unlike a W-CDMA system of the existing 3GPP Release 99/Release 4, the HS-DSCH uses a short transmission time interval (TTI) (3 slot, 2 ms) and supports diverse modulation code sets (MCS) and hybrid ARQ (HARQ) techniques in order to support a high data rate.
The HS-DSCH, a transport channel, of the HSDPA system, is mapped onto HS-PDSCH (High Speed Physical Downlink Shared Channel). The HS-PDSCH has been devised to transmit high speed user data to different users through each sub-frame.
FIG. 1 illustrates the construction of the HS-PDSCH. As shown in FIG. 1, the HS-PDSCH is constructed with 2 ms sub-frame and different users can share it for use through each sub-frame.
In order for a user equipment (UE=terminal) to receive a user data through the HS-DSCH, a shared control channel for HS-DSCH (HS-SCCH) and a dedicated physical channel (DPCH) should be constructed.
FIG. 2 illustrates a structure of a frame of a physical channel constructed in the dedicated physical channel (DPCH). With reference to FIG. 2, the DPCH is constructed with 10 ms—period (Tf) radio frame, and each frame includes 15 slots (Slot #0˜Slot #14). One slot length (Tslot) is 2560 chips, and a dedicated physical data channel (DPDCH) and a dedicated physical control channel (DPCCH) are alternately inserted in each slot.
In the DPCH, in turn from left, Ndata1 bit data (Data1) is included in the first DPDCH, a TPC (NTPC bit) and a TFCI (NTFCI) bit) are included in the first DPCCH, Ndata2 bit data (Data2) is included in the second DPDCH, and an Npilot bit pilot signal is included in the second CPCCH. The TFCI field includes size information of a data transmitted to a data field.
The HS-SCCH, a physical channel, is a type of a downlink common control channel to support the HS-DSCH. HS-SCCH transmits a UE ID (Identification) and control information so that the terminal can receive the HS-DSCH transmitting the high speed user data.
The UE ID and the control information are transmitted through each sub-frame (2 ms) of the HS-SCCH. The control information transmitted through the HS-SCCH is generated by a Node B (a base station) to which a cell transmitting the HS-DSCH belongs. The UE monitors the UE ID transmitted through the HS-SCCH to recognize whether there is a data to be received by itself and then receives a user data transmitted through HS-DSCH by using control information transmitted through HS-SCCH.
FIG. 3 is a structure of a sub-frame of HS-SCCH.
As shown in FIG. 3, HS-SCCH is constructed with a 2 ms sub-frame and different users can share it for use through each sub-frame. The control information that HS-SCCH transmits is roughly divided into transport format and resource related information (TFRI) and HARQ related information. The TFRI includes information related to a HS-DSCH transport channel set size, modulation, a coding rate and the number of multicodes, and the HARQ related information includes information such as a block number, a redundancy version. Besides, UE ID information representing user information is transmitted.
Each UE has an associated downlink DPCH, and as shown in FIG. 4, the terminal can receive maximum 4 HS-SCCHs.
FIG. 5 is a drawing illustrating a transmission timing of the HS-SCCH and the HS-DSCH. As shown in FIG. 5, after the UE ID and the control information are transmitted through the HS-SCCH, a data is transmitted through the HS-DSCH. The UE reads the control information transmitted through HS-SCCH and restores an HS-DSCH data. At this time, by enlarging an overlapping interval of the two channels as much as possible, a transmission delay can be reduced.
As mentioned above, in the case that a high speed user data is provided to different users through the HS-DSCH proposed in the HSDPA technique, at least one or more HS-SCCHs are configured in one cell. Especially, if there are many HSDPA terminals, configuration of plural HS-SCCHs in one cell ensures providing of an effective data service.
FIG. 6 illustrates a structure of a conventional UMTS radio access network (UTRAN). With reference to FIG. 6, UTRAN 112 has a structure that a serving RNC (SRNC) 114 and a drift RNC (DRNC) control base stations (Node B), respectively, and in soft handover, the UE (=mobile station) maintains a traffic channel with the base stations 118 and 120 located in the SRNC 114 and the DRNC 116.
A plurality of base stations (Node B) are placed under the SRNC 114 and the DRNC 116, and in occurrence of soft handover, the UE 122 can be simultaneously connected with each base station belonging to the SRNC 114 and the DRNC 116. The base station (Node B), SRNC 114 and DRNC 116 are connected through an Tub interface, and SRNC 114 and DRNC 116 are connected through an Iur interface. An interface between SRNC 114 and core network (CN) 110 is called ‘Iu’.
In general, the radio network controller (RNC) includes a control RNC (CRNC) (not shown) managing a common radio resource and a serving RNC (SRNC) 114 managing a dedicated radio resource allocated to each UE 122. The DRNC 116, existing in a drift radio network subsystem (DRNS), is a control station of a destination which provides a radio resource to the UE 122 if the UE 122 goes beyond the SRNC 114 and moves into its area.
In the UMTS system, transmission power of a common channel is determined by the CRNC, which manages a common radio resource. The power of the common channel determined by the CRNC is included in the data frame and transmitted to the base station (Node B) and the base station sets transmission power of the common channel on the basis of the transmission power value included in the data frame. Meanwhile, transmission power of a dedicated channel is determined by an SRNC which manages a dedicated radio resource. The power of dedicated channel as determined in the SRNC is included in a control frame and transmitted to the base station (Node B), and the base station sets transmission power of the dedicated channel on the basis of the transmission power value included in the control frame.
FIG. 7 illustrates a structure of a control frame used for updating a radio interface parameter in the UTRAN. With reference to FIG. 7, the control frame consists of a 2 byte flag field indicating whether there is a parameter, a 1 byte connection frame number (CFN), a 5 bit transmit power control (TPC) power offset (PO) and a 1 bit downlink power control (DPC) mode information field and is constructed with more than a 4 byte payload overall.
As stated above, in the current system, power of the common channel is controlled by the CRNC. HS-SCCH, a kind of the common channel, transmits information of different terminals through each sub-frame. Like the current system, if the CRNC manages power of HS-SCCH, the common channel, it is not possible for the CRNC to control power of HS-SCCH suitably to radio channel of each terminal. The reason is at least because the CRNC can not be aware of the radio channel condition of each terminal. Therefore, the current system can not effectively control power of HS-SCCH.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.